New Features
============
- Add `DictionaryCodec` that follows the same pattern as `RosMessageCodec`, but operates on generic Python dictionaries.  (!29)
  - (A less robust version of this used to be part of `ltcodecs` but was lost a while ago.) 

Bugfixes
========
- Fix a (functionally inconsequential) bug in the uint64 codec (it called `super()` on the wrong class, but one that still worked) (!33)
- Fix ROS2 array types (!30)

Testing
=======
- Fix some missing asserts in tests (!33)
- Use CI templates (!31)
- Pass the commit ref to the downstream `ros_acomms` pipeline so that the test uses this version. (!29, !31)

Documentation
=============
- Improved documentation.  Added quick start guides. (!32)